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PROBLEM 5: UNIT FIRES ON LOW FIRE, FAILS TO GO TO HIGH FIRE OPERATION
Flash Code
LED X + Y
Possible Cause Corrective Action/Comments
5.1
− Unit light s normally during low fire
− Call for high fire inducer switches to
high fire for 10 seconds then back to
low fire.
− Diagnostic lights flash the high
pressure switch failure to close.
LED 2 + 5
5.1.1
Prove switch does not close due to
obstruction in vent pipe.
ACTION 1 − Check for restricted vent. Remove all
blockage.
ACTION 2: Check for proper vent sizing. See
installation instructions.
5.1.2
Prove switch does not close due to
incorrect routing of the prove switch
line.
ACTION 1 − Check that the prove switch line is
correctly routed. Correctly route prove switch
line.
5.1.3
Prove switch does not close due to
obstructions in the prove switch line.
ACTION 1 − Remove any obstructions from the
the prove switch line and/or taps.
5.1.4
Prove switch line damaged
ACTION 1 − Check prove switch line for leaks.
Replace broken line if required.
5.1.5
Condensate in prove switch line.
ACTION 1 − Check prove switch line for conden-
sate. Remove condensate from line.
5.1.6
Prove switch does not close due to a
low differential prove across the
prove switch.
ACTION 1 − Check the differential pressure
across the prove switch. This pressure should
exceed the set point listed on the switch.
ACTION 2 − Check for restricted inlet vent. Re-
move all blockage.
ACTION 3 − Check for proper vent sizing and
run length. See installation instructions.
5.1.7
Wrong prove switch installed in the
unit, or prove switch is out of calibra-
tion.
ACTION 1 − Check that the correct prove switch
is installed in the unit. Replace prove switch if
necessary.
5.1.8
Miswiring of furnace or improper con-
nections at prove switch.
ACTION 1 − Check for correct wiring and loose
connections. Correct wiring and/or replace any
loose connections.
5.1.9
Prove switch failure.
ACTION 1 − If all the above modes of failure have
been checked, the prove switch may have failed.
Replace prove switch and determine if unit will
operate.
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